This present invention relates to an improved method of applying and centering an annular tread onto a pneumatic tire casing.
In the practice of retreading tires, more specifically when applying an annular tread or ring tread onto a pneumatic tire casing, it is common practice to stretch the tread prior to positioning it over the casing.
In U.S. Pat. No. 4,957,574, issued Sep. 18, 1990, a tread centering method and apparatus is disclosed. In that patent a tread expander is shown having a plurality of radially expandable fingers that support the tread at several locations and when expanded stretch the tread a sufficient amount to allow the tread to encircle the casing to which the tread is about to be mounted. This device requires the operator to position himself between the wheel mount assembly and the tread expander when he places the tread onto the expander. This means the operator of the equipment must work at the side of the apparatus and must lean into the equipment while holding an annular tread weighing as much as 50 pounds to place it on the unit. To avoid this, the operator often suspends the tread on one of the tread expander fingers to support the tread weight and then he simply works the tread over the remaining support fingers. This greatly reduces the fatigue and potential injury factor, but it in no way improves the time to make the assembly.
It is an objective of the present invention to provide a tread application apparatus that permits the operator to perform all operations at one end of the machine.
It is a further object of the invention to provide a machine with a unique tread alignment capability.
It is still a further objective to minimize worker fatigue by enabling a simpler method of applying the tread and casing to the apparatus.
An improved method for applying an annular tread to a pneumatic tire casing has the steps of mounting the tread on a tread expander assembly wherein the tread passes over a mount wheel prior to the casing being mounted onto the mount wheel. The mount wheel is movable along a line coincident with or parallel to the axis of the tread expander assembly. The method has the casing mounted to the mount wheel while the mount wheel is extended outward of the tread expander assembly, the tread is radially expanded and the mounted casing is retracted with the tread encircling the casing, clamping the tread to the casing and transferring the tread onto the casing.
The preferred method further has the step of mounting the tread on the tread expander, including the steps of pushing the tread along a first edge of the tread to a fixed distance at each location of tread support, thereby aligning the annular tread parallel to the casing prior to expanding the tread over the casing.
The improved apparatus for practicing the above described method has a control cabinet structure wherein all the mechanisms for supporting the casing and tread are extended from one end allowing the operator to work entirely in front of the apparatus.